Conveyors all over the world are in constant use handling a wide variety of usually solid materials that are in need of being transferred from one point to another. Materials include, but are not limited to, coal, sand, rocks, steeped corn, packages, and mined ores. Alternative means to conveyors for transporting solid materials include trucks or other vehicles, or conversion of the material to a slurry so that it may be pumped from one place to another.
Conveyors handling bulk solids such as coal or ores can extend across mountainous terrain, over roads and streams for many miles. These conveyors are made up of belts that are normally supported by three rollers positioned at the bottom and sides of the belt. One roller is usually horizontal and the two side rollers are at an angle of approximately 35 degrees from the horizontal plane.
Typically, the three rollers are supported by a frame that engages the shaft ends of the rollers (which shaft is generally concentric with the roller and of a slightly larger axial dimension than the roller) so as to keep the roller assemblies in line and in position for accommodating the belt and its load. The frames are normally positioned three feet or one meter from each other in a line, which equates to approximately 1,760 sets of three rollers per mile of conveyor run, or 1,100 sets per kilometer. Accounting for two bearing and bearing seals per roller, this approximation yields 10,560 bearings and bearing seals per mile of conveyor. Any one of the seals or bearings could severely degrade and cause the system to shut down. A stalled roller may put undue strain on the belt being used for holding the product, and when a bearing grinds to a halt, the resulting heat produced from the increased friction may initiate combustion of various combustible materials in and around the bearing location.
Rollers of the prior art are normally fitted with sealed bearings at either end. Sealed bearings have integral rubber sealing components on either side of the inner and outer race that contact the inner race in a frictional manner, often with a lubricant packed between the inner and outer races. At the axial extremity of the roller, rubber or composite seals are applied so as to protect the sealed bearings from dust, dirt, silicon or other foreign matter that may contaminate the bearings and their lubricant. The seals, so described, are of the contacting type and frictionally engaged with the stationary component of the roller, which is usually the stationary shaft, or the stationary seal component. As soon as wear occurs, sealing efficiency degrades so as to be completely ineffective. Reliability of the system suffers because of the very large number (as calculated above) of wearing and vulnerable components. The prior art contacting seals are prone to wear and are energy consumptive because of the frictional drag inherent in their design. This frictional drag increases the operating costs through increased maintenance and electrical energy costs; therefore, reliability and energy consumption must be addressed and are two of the integral and useful subjects of this invention. FIG. 1A presents an exploded view of a conveyor roller bearing arrangement known to those practiced in the art.
As taught by the prior art, conveyor rollers of this type are particularly suited to conveyors that operate in very difficult conditions. Typical environmentally difficult applications are mines, cement works, coal-fired electric utilities and dock installations, among others. The roller sealing system, as taught by the prior art, is designed to solve problems associated with the environmental challenges of dust, dirt, water, or other contaminants, low and high temperatures, or applications where a large temperature imbalance between day and night may be present. The principal task of the seals of the prior art used in conveyor rollers is to protect the primary bearing from harmful elements that may interfere with the primary bearing or impinge from the outside or the inside of the conveyor roller system and damage or shorten the useable life of the primary bearing. As found by applicant, the prior art fails to achieve the objective.
Given the large numbers of conveyor rollers typically installed and used, it is difficult for operators to be alerted to a primary bearing failure until a secondary event occurs. Many times, this secondary event is initiation of a smoldering fire or smoke from conveyed materials deposited in close proximity to the conveyor due to the heat often generated from primary bearing failure. This heat generation that may cause a smoldering fire typically occurs from ferrous metal to ferrous metal contact, as does sparking, both of which are allowed by primary bearing failure. The typical bearing seal is hidden from external inspection/view and is made of plastic so that it does not only conduct heat poorly but is prone to fail upon rapid heating from either combustion or ferrous metal to ferrous metal contact. As is well known to those practiced in the art, ferrous metal to ferrous metal contact (rubbing) may be severe enough to raise the metal temperatures to 2500 degrees Fahrenheit (1370 degrees Celsius) and result in partial or full melting of the primary bearing and the destruction thereof. Furthermore, this source of heat may support ignition of conveyed materials, such as the carbon in coal, which has a temperature of ignition in the range of 765 degrees Fahrenheit (407 degrees Celsius), in contact with or exposed to the primary bearing.